High Quality Content by WIKIPEDIA articles! The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core. Earth`s mantle is a rocky shell about 2,900 km (1,800 mi) thick that constitutes about 84% of Earth`s volume. It is predominantly solid and encloses the iron-rich hot core, which occupies about 15% of Earth`s volume. Past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface, upon which we live. Information about structure and composition of the mantle either result from geophysical investigation or from direct geoscientific analyses on Earth mantle derived xenoliths.